| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 91 === 【Abstract】
Lipopolysaccharide (LPS) is the toxic chemical component of the cell wall in all gram-negative bacteria which can stimulate immune cells, including macrophages and white blood cell, to release cytokines such as interleukin-1β, interleukin-6 and tumor necrosis factor-α. These pro-inflammatory mediators induce systemic acute inflammation and multiple organs dysfuction syndrome in sepsis. Plasma leakage from microvasculature is a hallmark of inflammation. Previous studies have demonstrated that other inflammatory agents, such as capsaicin, substance P and histamine could cause the acute formation of numerous endothelial gaps in the venules that result in extensive plasma leakage in the inflammatory tissues of the whole respiratory tract and a part of digestive tract in a few minutes. Mammalian intestines have many goblet cells that synthesize mucus and discharge it into the intestinal lumen. The mucus film that covers the surface epithelium facing the lumen of digestive system, is an immune defense that can prevent gastrointestinal epithelium from chemical and physical damage and act as a lubricant. Changes in goblet cell function and number are involved in microbial infection, inflammatory syndromes and immune factors. This study was aimed to investigate: (1) The degree of Plasma leakage and goblet cell hypersecretion in the small intestine of rats after an intravenous injection of a high dose of LPS (15 mg/kg), and (2) The involvement of vagus nerve and cholinergic receptors in plasma leakage and goblet cell secretion. For the study of plasma extravasation in small intestine during endotoxema, India ink was used as the tracer to mark the inflamed leaky microvessels. Rats were perfusion-fixed through the aorta, and endothelial gaps between endothelial cells of blood vessels were made visible with silver staining. The methacrylate sections of the ileum 3 μm in thickness were stained with Alcian blue and periodic acid-schiff reagent to detect glycoproteins of goblet cells. Our results showed that LPS not only caused an increase in plasma leakage but also triggered degranulation of many goblet cells in villi and crypts. Numerous gaps were found in postcapillary venules and collecting venules, and plasma extravasation was observed in the serosa and tunica muscularis rat small intestine after LPS. Extensive plasma extravasation occurred in earier phases (5-30 min). However, numerous goblet cells started to discharge mucus granules 30 min after LPS treatment. A large amount of extracellular mucus was accumulated between intestinal villi 1 hour after LPS stimulation. Pretreatment with atropine, the muscarinic receptor antagonist, significantly inhibited goblet cell secretion. The inhibitory effect of pretreatment with atropine or bilateral cervical vagotomy on LPS-induced plasma leakage was not consistent. It is concluded that the plasma leakage and goblet cell hypersecretion induced by endotoxin shock was time-dependent and was associated with activation of muscarinic cholinergic receptors.
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